The technology of the present disclosure relates to an image forming apparatus such as a printer, a copy machine, a facsimile, and a multifunctional peripheral thereof and a fixing device mounted in the image forming apparatus.
Conventionally, there has been proposed a fixing device capable of switching press-contact force between a fixing roller and a pressing roller abutting the fixing roller in an abutting state to first press-contact force and second press-contact force smaller than the first press-contact force. In this fixing device, while the press-contact force between both the rollers is set to the first press-contact force with respect to a normal paper, the press-contact force between both the rollers is set to the second press-contact force with respect to an envelope or a thin paper. In this way, wrinkles are prevented from occurring by excessive press-contact force applied to the envelope or the thin paper. In this fixing device, two springs are used in order to switch the press-contact force between both the rollers. When the press-contact force between both the rollers is set to the first press-contact force, resultant force of the two springs is applied to the pressing roller, and when the press-contact force between both the rollers is set to the second press-contact force, a pressing lever is released, so that the resultant force of the two springs applied to the pressing roller is made zero.